[1]} concluded that “adaptation to any stimulus is always acquired at a cost,
namely, at the cost of adaptation energy.” No other definition of adaptation energy was
given. This is just a resource of adaptability, which is spent in all adaptation
processes. The economical metaphors used by Selye, `cost' and `spending', were also
seminal and their use was continued in many works. For example, [2]}
considered adaptation energy as a “capital reserve of adaptation” and death as “a
bankruptcy in non-specific adaptation energy”.
